The present invention relates to a data symbol reading device for reading an encoded data symbol, such as a two dimensional data symbol.
Conventionally, there is known a data symbol reading device which can read product information in the form of a bar code. This type of data symbol reading device is commonly used with point of sale terminals to facilitate inventory control, etc. However, since the reading of bar codes only requires a one-dimensional scan along the length of the bar code, the amount of information that can be stored in a bar code is limited.
Recently, two types of data symbol reading devices, which can read a two dimensional tessellated data symbol affixed to a product, have been developed for use at point of sale terminals. The two types of data symbol reading devices employ different imaging devices. The first type of data symbol reading device uses an area sensor type of imaging device, such as a CCD. The CCD can read the entire pattern of the two dimensional data symbol without being moved with respect to the data symbol, and therefore the data symbol can be read quickly.
The second type of data symbol reading device uses a line sensor type of imaging device. The line sensor reads the data symbol line by line, and must be moved in a sub-scanning direction relative to the data symbol.
However, in the conventional data symbol reading device in which the area sensor is employed, since there is only one kind of light source for illuminating the data symbol, the usefulness of the data symbol reading device is limited.